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Computational design of graphitic carbon nitride photocatalysts for water splitting

Abstract

A series of structures based on graphitic carbon nitride (g-C3N4), a layered material composed of linked carbon-nitrogen heterocycles arranged in a plane, were investigated by density functional theory calculations. g-C3N4 is a semiconductor that absorbs UV light and visible light at the blue end of the visible spectrum, and is widely studied as a photocatalyst for water splitting; however, its photocatalytic efficiency is limited by its poor light-harvesting ability and low charge mobilities. Modifications to the g-C3N4 structure could greatly improve its optical and electronic properties and its photocatalytic efficiency. In this work, the g-C3N4 structure was modified by replacing the nitrogen linker with heteroatoms (phosphorus, boron) or aromatic groups (benzene, s-triazine and substituted benzenes). Two-dimensional (2D) sheets and three-dimensional (3D) multilayer structures with different stacking types were modelled. Several new structures were predicted to have electronic properties superior to g-C3N4 for use as water splitting photocatalysts. In particular, introduction of benzene and s-triazine groups led to band gaps smaller than in the standard g-C3N4 (down to 2.4 eV, corresponding to green light). Doping with boron in the linker positions dramatically reduced the band gap (to 1.7 eV, corresponding to red light); the doped material had the valence band position suitable for water oxidation. Our computational study showed that chemical modification of g-C3N4 is a powerful method to tune this material’s electronic properties and improve its photocatalytic activity.

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Supplementary files

Article information


Submitted
24 Dec 2019
Accepted
28 Jan 2020
First published
28 Jan 2020

Faraday Discuss., 2020, Accepted Manuscript
Article type
Paper

Computational design of graphitic carbon nitride photocatalysts for water splitting

G. O. Hartley and N. Martsinovich, Faraday Discuss., 2020, Accepted Manuscript , DOI: 10.1039/C9FD00147F

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